Hide public constructors
Implement IndexesOf action with tests
Move class to appropriate location
Implement IndexesOf.IgnoringCase action with tests

Also IndexesOf action was refactored by moving common logic to one place - CommonLogic class
Implement IndexesOf.From and IndexesOf.IgnoringCase.From actions with tests
Use FluentAssertions.ShouldThrow method instead of ExpectedException attribute
Refactor RemoveValues common logic to use new IndexesOf actions
Update comments for Insert actions
Extend constants

Sample value and marker were added
Extend extreme cases handling in Insert.Before action

Additional tests were added as well
Extend extreme cases handling in Insert.After action

Additional tests were added as well.
Both Before and After action extenders were refactored
Add more extreme cases tests for Insert actions
Extend extreme cases handling in Insert.BeforeOccurrence action

Additional tests were added as well
Fix bug with IgnoreCase extender for IndexesOf action

Also tests for marker at the beginning of the string were added
Extend extreme cases handling in Insert.BeforeOccurrence action

Additional tests were added as well.
Both Before and Before.From action extenders were refactored
Extend extreme cases handling in Insert.AfterOccurrence action

Additional tests were added as well
Extend extreme cases handling in Insert.AfterOccurrence.From action

Additional tests were added as well
Add missed test for Insert.BeforeOccurrence.From action

Tests marker at the beginning with the start point from the beginning case
Rename Before and After classes to BeforeAll and AfterAll for Insert action
Rename Before and After files to BeforeAll and AfterAll for Insert action